Recipe for a GX390 30+ hp on gas !

[flathead59]

I would like to hear everbodys input on a GX390 build that will push 30+ hp on pump gas ! Thanks Guys:thumbsup:

 

[minidragbike]

Stainless steel valves, stock size
32mm gas carb
HD rockers
.400" lift cam
Arc rod
Arc flywheel
3 stage header
Really good porting, and 60 pound dual springs
32 degrees timing

 

[flathead59]

Stainless steel valves, stock size
32mm gas carb
HD rockers
.400" lift cam
Arc rod
Arc flywheel
3 stage header
Really good porting, and 60 pound dual springs
32 degrees timing

Sounds good Charles , whats your take on using a 340 head , and what would you think a good light piston rod combo to use , And thanks again

 

[minidragbike]

We use these aftermarket quad pistons, they come in many larger bore sizes.

The 340 head gives you a little more compression, so it will make a little more power.

 

[Hothead79]

Stainless steel valves, stock size
32mm gas carb
HD rockers
.400" lift cam
Arc rod
Arc flywheel
3 stage header
Really good porting, and 60 pound dual springs
32 degrees timing

stock length rod?

 

[minidragbike]

stock length rod?

Yes, rod doesn't need to be longer to make more power.

 

[tis300c]

Where can I get a 3 stage header?...

 

[jakedmoe]

will the 390 rod and cam fit the 420?

 

[minidragbike]

will the 390 rod and cam fit the 420?

Depends on the model you have, they have some that everything is slightly different in size. But most are the same exact size. So you have to check and see for yourself.

 

[minidragbike]

Where can I get a 3 stage header?...

Robertson Torque Tubes can make you any header you want.

 

[HighDez760]

I'm not trying to thread jack and I do apologize ahead of time... I have the opurtunity of purchasing a gx390 for 25 bucks, they guy doesn't know if it runs it also seems like the messed around with the valves and were not able to figure it out on how it goes back together so lid is loose.. Other than that it turns freely.. Should I pop on it?

 

[Caseyslowgto]

I would especially if it's a real Honda

 

[HighDez760]

Yes real Honda and I forgot to mention the cover is missing where the pull start is.. I was able to identify it by the stamps on the block.. Thank you for the reply

 

[Caseyslowgto]

Check NR racing for factory parts and aftermarket

 

[Dave_In_Florida]

Should I pop on it?

No, you should buy it. You should only pop on it if you're a hayseed from Iowa with a funny accent and a TV program.

 

[HighDez760]

No, you should buy it. You should only pop on it if you're a hayseed from Iowa with a funny accent and a TV program.

Lay off the tv man..it's going to make your brain go to mush